1. Field of the Invention
The present invention relates to a silica powder which can be added to a recording material used for an ink jet printer. The present invention also relates to a method for producing the silica powder.
2. Background of the Invention
In recent years, ink jet printers have been widely used in homes and offices because they offer such advantages as low prices, quietness, low running costs, high printing quality and so on. Factors responsible for the widespread use of ink jet printers are that full-color and very fine images can be formed due to the astonishing advance of these printers, that the prices of ink jet printers are lower compared with color laser printers, and so on. Looking to the future, it appears that the demand for ink jet printers will increase more and more as computer penetration increases.
In an ink jet printer, an ink dye in an ink tank is ejected from a nozzle as droplets in accordance with an electrical signal from an computer to record a typeface or image on a recording material. A recording material for an ink jet printer can be formed by coating a transparent ink receiving layer on a base sheet. The base sheet includes a synthetic paper, a polyethylene terephthalate film, and so on. The ink-receiving layer comprises a binder, an inorganic oxide, water and so on as base materials, and can be formed by mixing these components in a slurry. The material for the binder is polyvinyl alcohol, and the inorganic oxide includes silica, alumina and so on. Upon contacting with the ink-receiving layer, the ink dye is absorbed by the binder and the inorganic oxide serves to inhibit the bleeding of the ink.
The properties required for the recording material for an ink jet printer are rapid absorption of the ink, no bleeding of the ink, brightness and sharpness of the resulting image, and so on.
Recently, demand for high definition of images has been increasing. In particular, in the case of printing of photographs, current recording materials for ink jet printers have problems such as bleeding of ink and unsatisfactory gradation in color.
Accordingly, there remains a need for recording materials for ink jet printers which overcome these disadvantages.
It is an object of the present invention is to provide a silica powder having a strong ability to adsorb an ink dye.
It is another object of the present invention to provide a method for producing such a silica powder.
The present invention provides a silica powder surface-treated with an epoxy compound having a plurality of epoxy groups. At least one of the epoxy groups of the epoxy compound is ring-opened and bound to the surface of the silica powder and at least a portion of the remaining epoxy groups of the epoxy compound are reacted with and bound to an amine compound. By using the silica powder thus produced as an additive for an recording material of an ink jet printer, the property of adsorbing an ink is increased and the smearing or bleeding of the ink can be prevented.
Without being limited to any particular theory, the inventive silica has amino groups on the surface thereof. When the silica powder is used as a base material of a recording material for an ink jet printer, the amino group on the surface of the silica powder, which has an electrically positive charge, can capture an ink dye, which has an electrically negative charge, on the surface of the silica powder. The ink dye component is not dispersed in a binder, and a bright and clear color can be formed. Accordingly, the surface-treated silica powder of the present invention strongly adsorbs an ink dye.